The present invention relates to a process and apparatus for reducing iron ore or the like.
In general, in the reduction of oxides, reductants or reducing gases are used. In order to reduce a large amount of oxides within a relatively short time, the oxides are charged into a reactor and the reducing gases are forced to flow through the reactor. This process has the problem that the uniform reduction of the charge cannot be attained as will be described in more detail with reference to FIGS. 1 and 2, showing the prior construction and operation.
Referring to FIG. 1, the lump ore 2 is charged through a top opening 3 of a fixed-bed type reactor 1 and then a top cover 4 is seatled. The reduced product is discharged through a bottom outlet 5 and a discharge or gate valve 6.
The reducing gas is charged through a pipe 7 with a valve 9 into the reactor 1 at the upper portion thereof and the spent gas is discharged from the bottom of the reactor 1 through a pipe 8 with a valve 10.
In operation, after the charge or iron ore 2 has been charged into the reactor 1, the valves 9 and 10 are opened. Then the reducing gas at high temperatures flows through the pipe 7 into the reactor 1 and through the bed of the lump ore 2 from the top A to bottom B and is discharged through the pipe 8. In this process, the charge 2 is reduced.
This process has the problem that the degree of metallization of the lump ore 2 at the top A of the bed is different from the degree of metallization of the lump ore 2 at the bottom B. As shown in the graph of FIG. 2, the degree E of metallization at the top A of the bed is higher than that at the bottom B. This means that the reduction of the lump ore 2 at the bottom B is slower than the reduction of the lump ore at the top A, which is closer to the reducing gas charging port.
It has been reported quantatively that when the degree E of metallization at the top A was 96.3%, the degree of metallization at the bottom B was 73.2%. It has been also reported that while the amount of the reducing gas required for attaining the average degree of metallization of 96% is 1 050 NM.sup.3 per ton of the total amount of reduced iron, while the amount for attaining the average degree of metallization of 92.4% is 1 250 NM.sup.3. It follows therefore that in order to increase the degree of metallization by 6.4%, the reducing gas must be increased by about 20%. That is, if the flow rate of the reducing gas is constant, the reduction time T would be increased by about 20%.
As described above, the batch of the reduced products varies in degree of metallization. In order to attain the desired qualities, the reduction time T must be increased, but the productivity drops inevitably.
The present invention overcomes the above and other problems encountered in the prior art batch reduction process A and the apparatus and has for its primary object to provide a reduction process and apparatus wherein the flow of the recuding gas or fluid in the charge of oxides to be reduced is reversed so that the oxides or charges both at the top A and bottom B of the bed may be reduced to a uniform degree, whereby the reduced product may have uniform qualities and the reduction time may be reduced. The present invention will become more apparent from the following description of some preferred embodiments thereof taken in conjunction with the accompanying drawings.